To improve the stability and to increase the load capacity, mobile cranes are usually provided with supporting measures. Such supporting measures comprise support bars protruding at the sides of the mobile crane, the support extensions being provided with support cylinders. By means of the support cylinders, a distal end may be supported on a ground area of the mobile crane to thereby enlarge the effective standing area. With the enlarged effective standing area, the load capacity, i.e., the maximum permissible load of the mobile crane can be improved.
Furthermore, to determine the load capacity, i.e., the maximum permissible load on the boom, load tables are provided in which the maximum permissible load is specified for each configuration of the mobile crane based on the possible degrees of freedom. In particular, the load tables consider the length and configuration, respectively, as well as the angle of rotation of the boom (usually 0-360°). The map-based determination of the maximum permissible load based on the load tables may be further supplemented by function-based models taking into account further parameters and which, e.g., consider the load capacity of the load rope.
Particularly for operation of the mobile crane on a narrow footprint, the support extensions may not be fully extended for use of the mobile crane, thus resulting in an asymmetrical support geometry of the resulting support positions. For mobile cranes with preset support geometries, in particular, when used with fully extended support extensions, the determination of the maximum permissible load can be sufficiently performed using conventional load tables in a known manner. However, in mobile cranes with variable support geometry, it is further necessary to consider the actual support positions of the mobile crane for determination of the maximum permissible load.
For scheduling, the maximum load capacities are usually provided as depending on various parameters, in particular on the load radius, as well as depending on the respective configuration. A crane operator can determine the operation of the crane, in particular, the configuration and possible lifting lengths of a load to be carried, before operation starts. For example, a mobile crane is disclosed in European Patent EP 1 444 162 B1 to Frankenberger et al., in which in an electronic control unit an operation area can be graphically displayed on a display based on one of the parameters of load and load radius as well as measure of a counterweight and counterweight radius.
From European patent publication EP 1 925 586 B1 to Morath, a mobile crane is known in which individual limit curves or limit values are stored for various parameters of the crane, wherein the individual limit curves or limit values may not be exceeded to ensure the safety of the crane operation or only be exceeded if an alarm signal is given. Furthermore, the mobile crane has measures to ensure crane safety, which are configured to monitor the individual limit curves or limit values of the various parameters with respect to exceeding. One of the limit curves represents the relation of the boom strength to the geometric degrees of freedom of the boom or based on this relation.
European patent publication EP 1 025 585 A1 to Hoffman discloses a mobile crane with a rotatable boom, wherein a total center of gravity of the crane and one or more tilting lines are determined. The stability of the crane is monitored. A signal is output and/or further movement of the crane prohibited or changed if the distance between the total center of gravity and a tilting line approaches or reaches a threshold value and/or if the ratio of the distance between the total center of gravity and the rotating assembly center to the distance between the tilting line from the rotating assembly center approaches or reaches a threshold value.
European patent document EP 2 674 384 A1 to Ruoss discloses a method for monitoring crane safety of a crane with a variable support base and a monitoring unit. Several safety criteria during crane operation are monitored where an allowable specific limit value is calculated and monitored on compliance during crane operation for each criterion, which depends on at least one parameter concerning the crane configuration or crane movement during crane operation.
Thus, a need exists to overcome the problems with the prior art systems, designs, and processes as discussed above.